Cationic Polymerization Of Cyclic Ethers Research Articles

Ring-opening polymerization processes involving activated monomer mechanism. Cationic polymerization of cyclic ethers containing hydroxyl groups.

Cationic polymerization of cyclic ethers containing hydroxyl groups as substituents is discussed in terms of contribution of Active Chain End (ACE) and Activated Monomer (AM) polymerization mechanisms.

Polymeric pyridinium salts as photoinitiators for cationic polymerization

Polymeric pyridinium salts were synthesized and used as photoinitiators for the cationic polymerization of cyclic ethers and vinyl ethers. A possible application of these salts as positive photoresists is also demonstrated.

Initiation of cationic polymerization of cyclic ethers by redox radical-chain reactions of onium salts

Redox radical-chain reactions of diaryliodonium halides (Ar 2 I + X) with THF and 1,3-dioxolane to give arenes (ArH) and iodoarenes (Ari) are reported. When the reactions are initiated by irradiation at 313 nm, the quantum yield for the formation of iodoarene is substantially greater than 1 (Φ ≃ 2-20). Nonphotochemical radical initiators give the same reaction, showing that the photochemical step is simply an initiation step. The key propagation step in these reactions is a single-electron reduction of the onium salts by ether-derived radicals: The photoinitiated reaction with THF follows zero-order kinetics, showing that termination does not compete with electron transfer

Activated monomer mechanism in the cationic polymerization of cyclic ethers

AbstractCationic polymerization of oxiranes proceeds in the presence of hydroxyl groups containing compounds by activated monomer (AM) mechanism, competing with active chain end (ACE) mechanism. According to the AM mechanism, propagation involves reaction of activated (e.g. protonated) monomer molecules with nucleophilic sites in the growing macromolecules. Active species are located on the monomer, and growing macromolecule is neutral; thus side‐reactions, typical for active chain‐ end mechanism, are suppressed. In the polymerization of ethylene oxide (EO) ether oxygen atoms along the chain are more exposed to the attack than in the polymers of substituted oxiranes and also react with protonated monomer. The contribution of these reactions, in comparison with propagation involving hydroxyl end groups, is analysed. The participation of the polymer units is highly restrained for chains with bulky substituents. In the AM polymerization of propylene oxide (PO) and epichlorohydrin (ECH), chain growth proceeds predominantly on the terminal hydroxyl groups. Syntheses of telechelic oligomers and macromonomers, applying the AM mechanism with protonated monomers, are described.

Ab‐initio electrostatic molecular potential contour maps for initiation step and Ab‐Initio MRD‐CI calculations for propagation step of cationic polymerization of oxetanes

AbstractThe initiation step in the cationic polymerization of cyclic ethers is influenced by basicity and ring strain. We carried out ab‐initio MODPOT/VRDDO/MERGE calculations on a variety of substituted oxetanes and generated electrostatic molecular potential contour (EMPC) maps in three‐dimensions around the molecules. The size of the negative EMPC map region around the oxygen enabled us to predict the propensity to polymerize prior to the syntheses of the actual monomers themselves. We carried out ab‐initio MODPOT/VRDDO/MERGE MRD‐CI calculations for the propagation step of oxetane reacting with protonated oxetanes to cause ring opening of protonated oxetane. Similar MRD‐CI calculations on variously substituted oxetanes will shed insight into relative copolymerization preferences.

Activated monomer propagation in cationic polymerizations

AbstractNew mechanism of cationic polymerization of cyclic ethers and acetals consisting in the activated (e.g. protonated) monomer addition to the electrically neutral macromolecule e.g.: magnified imageis discussed. It is shown, that when the ‐OH in the tail‐group is more nucleophilic than monomer itself this mechanism has chances to dominate over the traditional mechanism of propagation, involving tertiary oxonium ion.Kinetics of the polymerization process, elementary reactions, competition with the tertiary oxonium ion growth are discussed. Examples are given, based on the work on ethylene oxide and epichlorohydrin polymerization, showing how to apply the theory of the activated monomer in order to avoid side reactions, namely cyclization and disproportionation of the chains.

Distribution according to types of functionality of oligomers synthesized by cationic polymerization of cyclic ethers. Mathematical simulation

Mathematical simulation was used to investigate possibilities of using cationic polymerization of cyclic ethers to obtain reactive oligomers with a high content of functional end groups and cyclic products. It was shown that in the first case polymerization should be carried out with minimum possible monomer concentration, adding it to the system as it is used up. To obtain cyclic products a monomer concentration should be maintained in the system, which ensures maximum relative proportion of growing cations with a degree of polymerization equal to four. A formula was derived to determine optimum monomer concentration and its variation as products accumulate, based on rate constants of reactions taking place during cationic polymerization of cyclic ethers.

Molecular weight distribution of polymers as a method of investigating complex polymerization processes. Cationic polymerization of cyclic ethers

A study was made of the effect of reactions taking place during cationic polymerization of cyclic ethers on the variation of molecular weight distribution of polymers during polymerization. It was shown that this variation may be a means for establishing the type of reaction taking place. Ratios were derived to determine rate constants of the reactions studied using experimental results.

Spontaneous Cohabitory Anionic Polymerization of Vinylidene Cyanide and Cationic Polymerization of Cyclic Ethers on Mixing the Two Monomers at 25°

Spontaneous Cohabitory Anionic Polymerization of Vinylidene Cyanide and Cationic Polymerization of Cyclic Ethers on Mixing the Two Monomers at 25°

The role of water in the copolymerization of cyclic ethers

The general mechanism of action of water in the cationic polymerization of cyclic ethers on the molecular weigth (mol.wt.), composition and polydispersity of the products has been investigated. Water was found not to participate in the production of an active catalyst up to a certain concentration, not to cause decay, but to be utilized in the production of the hydroxyl end groups of the copolymer.

Cationic Polymerization of Cyclic Ethers Initiated by Macromolecular Dioxolenium Perchlorate

Cationic polymerization of tetrahydrofuran (THF) with 2-methyl-1,3-dioxoleum perchlorate proceeded as a living system without chain transfer and termination, and the initiation reaction was shown to be the bonding mechanism. Poly-THF with terminal dioxolenium perchlorate group was synthesized from poly(tetramethylene glycol) by stepwise reaction with adipoyl chloride, ethylene bromohydrin, and silver perchlorate. The quantitative formation of macromolecular dioxolenium salt was proved from the polymerization behavior of the THF. Polymerization of 3,3-bischloromethyloxetane by the initiator yielded block copolymer, and no chain-transfer reaction except the termination reaction was observed. Polymerization of 7-oxabicyclo[2.2.1]-heptane by the initiator yielded homopolymer as well as block copolymer, and a significant amount of chain transfer reaction was observed. Polymerizatian of dioxolane and tetraoxane by the initiator yielded little block copolymer, demonstrating the different mechanism of the initiation reaction in the case of cyclic formals.

Polymerization of Cyclic Ethers

Abstract In the present series of studies on the cationic polymerization of cyclic ethers, the reactivities of cyclic ethers were quantified and the effect of the catalyst upon the polymerization kinetics was revealed. These kinetic analyses were successfully performed by means of our “phenoxyl end-capping method”. The change of the reactivity by the ring size of the monomer was interestingly demonstrated. In addition, it is emphasized that the frequency factor as well as the activation energy influence the rate constant of propagation. As to the effect of catalyst upon the polymerization kinetics, the most important conclusion is that the rate constant of propagation changes very little according to the changes of the catalyst components. Variation of the conversion rate by a change of catalyst is due to differences in the rates of the initiation and the termination reactions.

The role of intermolecular hydride transfer in initiation and chain transfer in the cationic polymerization of cyclic ethers

The role of intermolecular hydride transfer in initiation and chain transfer in the cationic polymerization of cyclic ethers

Kinetics and mechanism of cationic polymerization of cyclic ethers in the presence of aldehyde additives

Kinetics and mechanism of cationic polymerization of cyclic ethers in the presence of aldehyde additives

Regularities of cationic polymerization of cyclic ethers

Regularities of cationic polymerization of cyclic ethers

Some kinetic and mechanistic consequences of chain transfer to polymer in the cationic polymerization of cyclic ethers and acetals

Some kinetic and mechanistic consequences of chain transfer to polymer in the cationic polymerization of cyclic ethers and acetals

Kinetics and mechanism of the exchange interaction of trialkyloxonium salts with esters

1. The kinetics of the exchange of triethyloxonium hexachloroantimonate with butyl acetate in nitrobenzene solution in the temperature interval 30–70°C, simulating the chain transfer in the cationic polymerization of cyclic ethers on transfer agents containing an ester functional group, was investigated. 2. A mechanism of the process, the feature of which is the formation of an intermediate complex compound of the type of an oxonium salt, which in turn is formed through a cyclic donor — acceptor transition complex, was proposed. 3. The kinetic data obtained give a direct confirmation of our earlier conclusion of an oxonium nature of the growing active centers in the cationic polymerization of cyclic ethers and other oxygen-containing heterocycles.

Kinetics and mechanism of cationic polymerization of cyclic ethers with polyester additives

Kinetics and mechanism of cationic polymerization of cyclic ethers with polyester additives

環状エーテルのカチオン重合における促進剤

環状エーテルのカチオン重合における促進剤